That is a very good RAM size if you are running a 32-bit OS like any of the recent Windows versions - XP, Vista, Win 7. You actually cannot use more than about 3.5 GB of RAM (and nobody installs that extra 0.5 GB!) unless you are using a 64-bit version of the OS.
Another factor is how your video is being done. If you are using only motherboard main RAM for video provided by a chip on the motherboard, then going up to 4 GB of RAM will give you a bit more space to use. But if you have an add-on video card in the PCI slots and are NOT using mobo video, there is NO advantage to more RAM unless you go to a 64-bit OS.